fenretinide and Sarcoma--Ewing

Overexpression of plasma membrane multi-drug resistance protein 1 (MRP-1) can lead to multidrug resistance. In this study, we describe for the first time the expression of mitochondrial MRP-1 in untreated human normal and cancer cells and tissues.. MRP-1 expression and subcellular localisation in normal and cancer cells and tissues was examined by differential centrifugation and western blotting, and immunofluorescence microscopy. Viable mitochondria were isolated and MRP-1 efflux activity measured using the calcein-AM functional assay. MRP-1 expression was increased using retroviral infection and specific overexpression confirmed by RNA array. Cell viability was determined by trypan blue exclusion and annexin V-propidium iodide labelling of cells.. MRP-1 was detected in the mitochondria of cancer and normal cells and tissues. The efflux activity of mitochondrial MRP-1 was more efficient (55-64%) than that of plasma membrane MRP-1 (11-22%; P<0.001). Induced MRP-1 expression resulted in a preferential increase in mitochondrial MRP-1, suggesting selective targeting to this organelle. Treatment with a non-lethal concentration of doxorubicin (0.85 nM, 8 h) increased mitochondrial and plasma membrane MRP-1, increasing resistance to MRP-1 substrates. For the first time, we have identified MRP-1 with efflux activity in human mitochondria.. Mitochondrial MRP-1 may be an exciting new therapeutic target where historically MRP-1 inhibitor strategies have limited clinical success.

Topics: Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Biological Transport, Active; Cell Line, Tumor; Cell Membrane; Dactinomycin; Doxorubicin; Drug Resistance, Neoplasm; Etoposide; Fenretinide; Fluoresceins; Fluorescent Dyes; Gene Expression; HSP70 Heat-Shock Proteins; Humans; Membrane Proteins; Mitochondria; Protein Transport; Sarcoma, Ewing; Vincristine

Glutathione (GSH) is implicated in drug resistance mechanisms of several cancers and is a key regulator of cell death pathways within cells. We studied Ewing's sarcoma family of tumours (ESFT) cell lines and three mechanistically distinct anticancer agents (fenretinide, doxorubicin, and vincristine) to investigate whether the GSH antioxidant system is involved in the reduced sensitivity to these chemotherapeutic agents in hypoxia. Cell viability and death were assessed by the trypan blue exclusion assay and annexin V-PI staining, respectively. Hypoxia significantly decreased the sensitivity of all ESFT cell lines to fenretinide-induced death, whereas the effect of doxorubicin or vincristine was marginal and cell-line-specific. The response of the GSH antioxidant system in ESFT cell lines to hypoxia was variable and also cell-line-specific, although the level of GSH appeared to be most dependent on de novo biosynthesis rather than recycling. RNAi-mediated knockdown of key GSH regulatory enzymes γ-glutamylcysteine synthetase or glutathione disulfide reductase partially reversed the hypoxia-induced resistance to fenretinide, and increasing GSH levels using N-acetylcysteine augmented the hypoxia-induced resistance in a cell line-specific manner. These observations are consistent with the conclusion that the role of the GSH antioxidant system in modulating the sensitivity of ESFT cells to fenretinide is heterogeneous depending on environment and cell type. This is likely to limit the value of targeting GSH as a therapeutic strategy to overcome hypoxia-induced drug resistance in ESFT. Whether targeting the GSH antioxidant system in conjunction with other therapeutics may benefit some patients with ESFT remains to be seen.

Topics: Acetylcysteine; Antineoplastic Agents; Antioxidants; Apoptosis; Cell Count; Cell Hypoxia; Cell Line, Tumor; Cell Proliferation; Cell Survival; Dietary Supplements; Drug Screening Assays, Antitumor; Fenretinide; Gene Knockdown Techniques; Glutathione; Humans; Inhibitory Concentration 50; Intracellular Space; Models, Biological; Reactive Oxygen Species; RNA, Small Interfering; Sarcoma, Ewing

Sustained p38(MAPK) phosphorylation upregulates p75 neurotrophin (p75(NTR)) and induces apoptosis in Ewing's sarcoma family of tumours (ESFT). As fenretinide induces ESFT death through sustained p38(MAPK) phosphorylation, we hypothesised that this may be effected through upregulation of death receptors (DRs) and that treatment of fenretinide plus DR ligands may enhance apoptosis.. DR expression was determined by flow cytometry. Trypan blue exclusion assays, caspase-8 flow cytometry and immunoblotting for Bid were used to measure cell death.. Fenretinide upregulated cell surface expression of tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors, FAS and p75(NTR), in an ASK1- and p38α-dependent manner. Cotreatment with fenretinide and DR ligands resulted in synergistic death compared with either agent alone; caspase-8 and Bid were cleaved in a time-dependent manner. Fenretinide did not increase DR expression in non-malignant cells. Furthermore, fenretinide, TRAIL or a combination of both agents was non-cytotoxic to non-malignant cells. Etoposide and actinomycin D increased expression of all DRs examined, whereas vincristine increased FAS alone. Only actinomycin D and TRAIL, and etoposide with TRAIL or FasL, enhanced death compared with either agent alone.. The synergistic death observed with fenretinide and DR ligands suggests that this combination may be an attractive strategy for the treatment of ESFT.

Topics: Cell Death; Cell Line, Tumor; Fenretinide; Humans; MAP Kinase Kinase Kinase 5; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Receptors, Death Domain; Sarcoma, Ewing; TNF-Related Apoptosis-Inducing Ligand; Up-Regulation

Ewing's sarcoma family of tumours (ESFT) are childhood cancers whose aggressive behaviour and propensity to relapse prompts the need for new treatment approaches. In this study, the role of cellular antioxidants in determining the sensitivity of ESFT cell lines to the cytotoxicity of the antineoplasic agent fenretinide was investigated with a view to identifying targets for the development of new treatment strategies. ESFT cell lines differentially express cellular antioxidants, although cellular glutathione (GSH) was identified as the major determinant of sensitivity to fenretinide. The importance of GSH in ESFT physiology was demonstrated by the depletion of intracellular GSH using l-buthionine (S,R) sulphoximine (BSO), which decreased cell viability. Furthermore, pre-treatment of ESFT cells with BSO sensitised them to fenretinide-induced death. Overall, these results demonstrate that ESFT cells are sensitive to changes in intracellular redox environment, and that targeting specific cellular antioxidants might be a viable strategy in treating ESFT.

Topics: Antineoplastic Agents; Antioxidants; Bone Neoplasms; Buthionine Sulfoximine; Cell Death; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fenretinide; Glutathione; Humans; Oxidation-Reduction; Oxidative Stress; Oxidoreductases; Reactive Oxygen Species; Sarcoma, Ewing; Tumor Cells, Cultured

The Ewing's sarcoma family of tumours (ESFT) are small round cell tumours characterized by the non-random EWS-ETS gene rearrangements. We have previously demonstrated that ESFT are highly sensitive to fenretinide-induced death, effected in part through a reactive oxygen species (ROS)-dependent pathway. Here, we demonstrate for the first time that the sensitivity of ESFT cells to fenretinide-induced cell death is decreased following downregulation of the oncogenic fusion protein EWS-Fli1; siRNA targeting EWS-Fli1 attenuated fenretinide-induced cell death in cell lines expressing EWS-Fli1, but not EWS-ERG. This decrease in cell death was independent of the level of ROS produced following exposure to fenretinide, but was effected through EWS-Fli1-dependent modulation of p38(MAPK) activity. Furthermore, inhibition of p38(MAPK) activity and knockdown of EWS-Fli1 reduced fenretinide-induced mitochondrial permeabilization, cytochrome c release, caspase and PARP cleavage, consistent with the hypothesis that p38(MAPK) is critical for activation of the death cascade by fenretinide in ESFT cells. These data demonstrate that expression of EWS-Fli1 enhances fenretinide-induced cell death in ESFT and that this is effected at least in part through modulation of p38(MAPK) activity.

Topics: Antineoplastic Agents; Apoptosis; Blotting, Western; Caspases; Cell Proliferation; Cytochromes c; Down-Regulation; Electroporation; Fenretinide; Flow Cytometry; Gene Expression Regulation, Enzymologic; Humans; Membrane Potentials; Mitochondria; Oncogene Proteins, Fusion; p38 Mitogen-Activated Protein Kinases; Poly(ADP-ribose) Polymerases; Proto-Oncogene Protein c-fli-1; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; RNA-Binding Protein EWS; RNA, Small Interfering; Sarcoma, Ewing; Transcription Factors; Tumor Cells, Cultured

The role of NF-kappaB in the Ewing's sarcoma family of tumours (ESFT) and their response to fenretinide has been investigated. Basal levels of phosphorylated NF-kappaB were low in all ESFT cells. BAY 11-7082 decreased cell viability, which was accompanied by caspase-3 cleavage. This was independent of the increase in reactive oxygen species, p38(MAPK) phosphorylation and expression of NF-kappaB target proteins. NF-kappaB knockdown did not induce death under normal growth conditions, but did reduce TNFalpha-dependent cell survival. Fenretinide-induced apoptosis was independent of NF-kappaB. BAY 11-7082-induced cell death through an NF-kappaB-independent mechanism and enhanced cell death when combined with fenretinide.

Topics: Apoptosis; Bone Neoplasms; Cell Line, Tumor; Fenretinide; Humans; I-kappa B Proteins; NF-kappa B; NF-KappaB Inhibitor alpha; Nitriles; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Reactive Oxygen Species; Sarcoma, Ewing; Sulfones; Transcription Factor RelA; Tumor Necrosis Factor-alpha

There is an urgent need for new therapeutic strategies in Ewing's sarcoma family of tumors (ESFT). In this study, we have evaluated the effect of fenretinide [N-(4-hydroxyphenyl)retinamide] in ESFT models.. The effect of fenretinide on viable cell number and apoptosis of ESFT cell lines and spheroids and growth of s.c. ESFT in nu/nu mice was investigated. The role of the stress-activated kinases p38(MAPK) and c-Jun NH(2)-terminal kinase in fenretinide-induced death was investigated by Western blot and inhibitor experiments. Accumulation of reactive oxygen species (ROS) and changes in mitochondrial transmembrane potential were investigated by flow cytometry.. Fenretinide induced cell death in all ESFT cell lines examined in a dose- and time-dependent manner. ESFT cells were more sensitive to fenretinide than the neuroblastoma cell lines examined. Furthermore, fenretinide induced cell death in ESFT spheroids and delayed s.c. ESFT growth in mice. p38(MAPK) was activated within 15 minutes of fenretinide treatment and was dependent on ROS accumulation. Inhibition of p38(MAPK) activity partially rescued fenretinide-mediated cell death in ESFT but not in SH-SY5Y neuroblastoma cells. c-Jun NH(2)-terminal kinase was activated after 4 hours and was dependent on ROS accumulation but not on activation of p38(MAPK). After 8 hours, fenretinide induced mitochondrial depolarization (Deltapsi(m)) and release of cytochrome c into the cytoplasm in a ROS- and p38(MAPK)-dependent manner.. These data show that the high sensitivity of ESFT cells to fenretinide is dependent in part on the rapid and sustained activation of p38(MAPK). The efficacy of fenretinide in preclinical models demands the evaluation of fenretinide as a potential therapeutic agent in ESFT.

Topics: Animals; Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Cell Survival; Cytochromes c; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fenretinide; Flow Cytometry; Humans; Imidazoles; Intracellular Membranes; JNK Mitogen-Activated Protein Kinases; Membrane Potentials; Mice; Mice, Nude; Mitochondria; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Pyridines; Reactive Oxygen Species; Sarcoma, Ewing; Xenograft Model Antitumor Assays

Patients with disseminated Ewing's family of tumors (ESFT) often experience drug-resistant relapse. We hypothesize that targeting minimal residual disease with the cytotoxic retinoid N-(4-hydroxyphenyl) retinamide (4-HPR; fenretinide) may decrease relapse. We determined the following: (a) 4-HPR cytotoxicity against 12 ESFT cell lines in vitro; (b) whether 4-HPR increased ceramide species (saturated and desaturated ceramides); (c) whether physiological hypoxia (2% O(2)) affected cytotoxicity, mitochondrial membrane potential (DeltaPsi(m)) change, or ceramide species or reactive oxygen species levels; (d) whether cytotoxicity was enhanced by l-threo-dihydrosphingosine (safingol); (e) whether physiological hypoxia increased acid ceramidase (AC) expression; and (f) the effect of the AC inhibitor N-oleoyl-ethanolamine (NOE) on cytotoxicity and ceramide species. Ceramide species were quantified by thin-layer chromatography and scintillography. Cytotoxicity was measured by a fluorescence-based assay using digital imaging microscopy (DIMSCAN). Gene expression profiling was performed by oligonucleotide array analysis. We observed, in 12 cell lines tested in normoxia (20% O(2)), that the mean 4-HPR LC(99) (the drug concentration lethal to 99% of cells) = 6.1 +/- 5.4 microm (range, 1.7-21.8 microm); safingol (1-3 microm) synergistically increased 4-HPR cytotoxicity and reduced the mean 4-HPR LC(99) to 3.2 +/- 1.7 microm (range, 2.0-8.0 microm; combination index < 1). 4-HPR increased ceramide species in the three cell lines tested (up to 9-fold; P < 0.05). Hypoxia (2% O(2)) reduced ceramide species increase, DeltaPsi(m) loss, reactive oxygen species increase (P < 0.05), and 4-HPR cytotoxicity (P = 0.05; 4-HPR LC(99), 19.7 +/- 23.9 microm; range, 2.3-91.4). However, hypoxia affected 4-HPR + safingol cytotoxicity to a lesser extent (P = 0.04; 4-HPR LC(99), 4.9 +/- 2.3 microm; range, 2.0-8.2). Hypoxia increased AC RNA expression; the AC inhibitor NOE enhanced 4-HPR-induced ceramide species increase and cytotoxicity. The antioxidant N-acetyl-l-cysteine somewhat reduced 4-HPR cytotoxicity but did not affect ceramide species increase. We conclude the following: (a) 4-HPR was active against ESFT cell lines in vitro at concentrations achievable clinically, but activity was decreased in hypoxia; and (b) combining 4-HPR with ceramide modulators synergized 4-HPR cytotoxicity in normoxia and hypoxia.

Topics: Acetylcysteine; Antineoplastic Agents; Antioxidants; Apoptosis; Cell Hypoxia; Ceramides; Drug Synergism; Enzyme Inhibitors; Fenretinide; Galactosylgalactosylglucosylceramidase; Gene Expression Profiling; Humans; Membrane Potentials; Mitochondria; Neoplasm, Residual; Neuroectodermal Tumors, Primitive; Oligonucleotide Array Sequence Analysis; Protein Kinase C; Reactive Oxygen Species; Sarcoma, Ewing; Sphingosine; Tumor Cells, Cultured